1. Field of the Invention
The present invention relates to a surface texture measuring machine for measuring surface profiles, surface roughness and the like of an object to be measured and a surface texture measuring method. Specifically, the present invention relates to a surface texture measuring machine including a contact-type detector provided with a stylus and an image probe, and a surface texture measuring method.
2. Description of Related Art
There has been known a surface texture measuring machine in which a stylus is moved along a surface of an object while being in contact with the surface of the object. A displacement of the stylus due to a surface profile or surface roughness of the object is detected, thereby measuring the surface profile, surface roughness and the like of the object based on the displacement of the stylus (see, for instance, Patent Literature: JP-A-05-087562).
In such a typical surface texture measuring machine, in order to measure the surface profile, surface roughness and the like of the object, while visually checking and adjusting a relative position between a tip end of a stylus and a measurement area on the object, an operator sets the tip end of the stylus at a measurement starting position on the object and then moves the stylus along the surface of the object. A surface texture such as the surface profile and the surface roughness of the object is measured based on a vertical displacement of the stylus due to the surface profile, surface roughness and the like of the object.
Moreover, in the surface texture measuring machine, when an attitude of the object is inclined relative to a measurement axis in measuring a surface of the object, a measurement result may have an error. For instance, when an attitude of a cylinder is inclined relative to a measurement axis in measuring an axial texture of a surface of the cylinder, a stylus is displaced in an outer circumferential direction of the cylinder as well as in an axial direction of the cylinder while the stylus is moved along the measurement axis. For this reason, a measurement value includes a value showing an outer circumferential texture of the cylinder as well as a value showing an axial concavity and convexity of the surface of the cylinder, so that the measurement result has an error. Moreover, in the surface texture measuring machine, when a to-be-measured surface is inclined relative to a horizontal plane, the measurement result may also have an error.
Accordingly, there has been developed a surface texture measuring machine that performs a preliminary measurement of an object with a stylus before an actual measurement and adjusts an attitude of the object, for instance, in parallel to a measurement axis based on a result of the preliminary measurement (for instance, Patent Literature 2: JP-A-2000-266534). The surface texture measuring machine of Patent Literature 2 includes a turntable that rotates the object on a horizontal plane. The surface texture measuring machine rotates the turntable based on the result of the preliminary measurement performed with the stylus and adjusts the attitude of the object in parallel to the measurement axis (so-called alignment).
Also, the surface texture measuring machine of Patent Literature 2 includes a leveling table that inclines the object relative to the horizontal plane. The surface texture measuring machine inclines the leveling table based on the result of the preliminary measurement performed with the stylus and adjusts the attitude of the object so that the to-be-measured surface thereof is horizontal (so-called leveling).
Due to a recent tendency for measuring minute and thin objects, objects or measuring spots are downsized. Accordingly, the above setting operation of a stylus, which is quite complicated and requires a long time, places a large burden on the operator.
In addition, some types of objects may interfere with (collide with) a stylus to damage the stylus or the objects.
Particularly, as shown in FIGS. 18A to 18C, in measuring a radius or diameter of each of a plurality of microlens molding surfaces 72 having convexity (or concavity) of 1 mm or less diameter that are formed on a microlens array mold 71, the stylus must correctly trace a center line where vertexes (peak or bottom points) of the microlens molding surfaces 72 are located in order to obtain a correct measurement result.
In order to measure such an object, as shown in FIGS. 19A to 19C, in a typical measurement, the operator is required to position a tip end of a stylus 24 on the microlens molding surface 72 while visually checking a relative position between the tip end of the stylus 24 and the microlens molding surface 72 (see FIG. 19A), to move a stage on which the microlens array mold 71 (the object) is mounted (see FIG. 19B), to detect the vertex of the microlens molding surface 72 (see FIG. 19C), and to relatively move the stylus 24 so as to trace the center line of the microlens molding surface 72.
For this reason, in a typical operation, a setting time of the stylus is extremely longer than a measuring time (for instance, the measuring time is approximately 10 seconds and the setting time is approximately 120 seconds).
Moreover, in the surface texture measuring machine of Patent Literature 2, it takes extremely long time for the preliminary measurement because the preliminary measurement requires many steps and uses the stylus for measuring the surface of the object. Further, the object may be damaged by the stylus.